For decades, plaques have been posted in elevator lobbies urging occupants to use the stairs during a fire. However, it took only 16 minutes on Sept. 11th, 2001 to call into question almost a century of conventional wisdom. In those 16 minutes before the second tower at the World Trade Center was struck, nearly 3,000 occupants were able to evacuate to safety because they USED the elevators.
image by Jonathan Ford
Last September marked the ninth anniversary of the World Trade Center Towers tragedy, prompting some to consider how far we have come in dealing with the aftermath of that attack and the proposed building code modifications that could potentially save lives during the evacuation of very tall buildings.
One of those proposals, occupant-evacuation elevators as a secondary means of egress to stairs, has gained popularity - and a reference in the 2009 International Building Code - and have already been used in Freedom Tower (United Arab Emirates) and in modified form in such buildings as One Financial Center Shanghai and Stratosphere Tower (Las Vegas).
Separately, the National Fire Protection Association (NFPA) added 'Annex B' to the NFPA 101 Life Safety Code that defines how occupant-evacuation elevators should be designed as a voluntary provision.
This Shift Marks the Beginning of a Growing Trend
Under the 2009 International Building Code (IBC), buildings taller than 75 feet are now required to have an elevator large enough to accommodate a stretcher. Buildings taller than 120 feet are required to have a special fire service elevator, and buildings taller than 420 feet need to have either a third stairwell or occupant-evacuation elevators.
Among the changes NFPA made: elevator lobbies need to be enclosed and located directly adjacent to an exit stairwell, and may also grow in size to accommodate occupants who have gathered for an evacuation. Sprinklers are also prohibited from evacuation elevator machine rooms.
So, why were elevators banned from use a public egress in the first place?
Triangle Shirtwaist Factory
It was on March 25th, 1911, that the most famous case of elevator evacuation failure occurred. The Triangle Shirtwaist Company was located on the top three floors (8th, 9th, and 10th) of the Asch building in New York City, a structure which remains standing today. A fire in a rag bin caused panic for the 500 sweatshop workers who occupied these floors.
The elevator operations saved many lives by travelling three times up to the ninth floor for passengers, but they were eventually forced to give up when the rails of one of the two elevators buckled under the heat. Some victims pried the elevator doors open and jumped down the empty shaft in a desperate attempt to avoid the flames. The weight of these bodies made it impossible for the elevators to make another attempt. In total, 147 people died, many within the first 15 minutes of the start of the fire.
Elevator Operation and Fires
Today, evacuation elevators can make it easier for mobility-impaired occupants to evacuate a building, and make it faster for those who need to use the stairwells to evacuate by speeding the overall flow, some experts say.
However, elevator use is currently governed by the American Society of Mechanical Engineers (ASME) A17 Life Safety Code for Elevators and Escalators.The problem is that while NFPA and ICC have made code changes that begin to define evacuation elevators, ASME has not. Under ASME standards, once a fire has been detected elevators still operate under either Phase I or Phase II regulations.
Under Phase I operation, elevators that are 25 feet or more above the main floor return either to a designated landing area or an alternate area. Phase I operation is activated either manually by a special key or automatically by a fire alarm initiating device. A sensor can detect smoke in the hoist-way, lobby or machine room and trigger Phase I. The goal is to remove the elevators from service so that building occupants DO NOT use elevators during a fire and become trapped.
Phase II operation is an override meant for firefighters after Phase I has been activated. Under Phase II operation, firefighters can use a key-switch to operate the elevator, provided the hoist-way is clear of smoke and the elevator has electricity.
Since 2004, ASME has been conducting a hazard analysis to determine how elevators might be safely used for evacuations. A related analysis is looking at whether fire fighters could use protected elevators to move close to a fire. Engineers from across the country are rethinking the traditional stairwell-centered approach to emergency egress from buildings and embracing a more holistic strategy that includes all aspects of building design and operation, as well as their impacts on occupant safety.
This December, the ASME is conducting a symposium on the use of elevators in fires and other emergencies, held in Orlando, Florida. Sponsors of this symposium include the National Institute of Standards and Technology (NIST), NFPA, and other related organizations. They are focusing on the progress of the ASME/a17 Task Group on the Use of Elevators by Firefighters and Use of Elevators for Occupant Egress, as well as well as reviewing the code changes under development that affect elevator, building, and life safety codes.
It appears that evacuation elevators are going to become another tool in making high-rises safer, if not an outright requirement in some cases. ASME, ICC and NFPA are all moving towards that same destination.
Christopher E. Chwedyk, CSI, AIA is a licensed architect, Director and Chief Code Consultant of the Code Group at Burnham Nationwide in Chicago. He was previously the principal of Gage-Babcock and Associates; a firm specializing in fire protection engineering. With more than 33 years of experience in the architectural field, Mr. Chwedyk has performed numerous code compliance plan reviews for the City of Chicago and other municipalities. He has a BArch degree from UIC and a Masters of Project Management (MPM) from the Keller Graduate School of Management. An adjunct faculty member of Harper College since 1998, Chris teaches courses on building codes and construction drawings.